"“Being impulsive with money" and "being dedicated to one's music," "being talkative at lunch," or "being conscientious in one's research" are also, of course, character traits. They are, however, situation-specific or local traits rather than global personality features that manifest themselves across the board in all situations. Contrary to folk psychology, systematic studies find very low levels of cross-situational consistency for character traits. Although correlations exist, they are typically so low that they cannot be detected "by the naked eye." Psychopaths may exhibit uncaring behavior across the board, and the younger Cato may have been consistently heroic, but for the great majority of individuals who fall between these extremes such consistency is not to be expected. The more extreme idea of folk psychology, according to which all virtues go together, has not been as thoroughly tested, perhaps because it seems so obviously implausible. Yet it may still have a grip on the mind, as shown by our confidence in the medical skills of doctors who have good "bedside manners." In classical antiquity, the idea that excellence in one arena was an infallible predictor or "index" of excellence in others was common. Psychologists refer to this as a "halo effect."

Often, therefore, the explanation of behavior is found in the situation rather than in the person. Consider for instance the fact that some Germans acted to rescue Jews from the Nazi regime. On a "character-ological" theory, one would assume that the rescuers had an altruistic personality type that nonrescuers lacked. It turns out, however, that the factor with the strongest explanatory power was the "situational" fact of being asked to rescue someone. The causal link could arise in two ways. On the one hand, it is only by being asked that one can obtain the information that is needed to act as a rescuer. On the other hand, the face-to-face situation of being asked might trigger acceptance because of the shame one would feel if one refused. The first explanation assumes altruism but denies that it is sufficient to explain the behavior. The second denies altruism and substitutes social norms for moral norms. On either account, what differentiates rescuers from nonrescuers is the situation in which they find themselves rather than their personality.

The Kitty Genovese case is another real-life example of the power of the situation. It is implausible to stipulate, on the basis of their inaction, that all the witnesses to her murder were callous and indifferent to human suffering. Rather, many of them may have thought that someone else was going to call the police, or that since nobody was doing anything about it the situation was not as serious as it might seem ("probably just a domestic dispute"), or that the inaction of the others suggested that direct intervention might be risky. These lines of reasoning become more plausible the greater the number of passive bystanders. Thus in one experiment, subjects heard a confederate of the experimenter feigning an epileptic seizure over the intercom system. When subjects believed they were the only listener, 85 percent intervened to help; when they believed there was one other listener, 62 percent intervened; when they believed there were four others, 31 percent intervened. In another experiment, 70 percent of lone bystanders intervened but only 7 percent did so when sitting next to an impassive confederate. With two naive subjects, the victim received help in 40 percent of the cases. Thus not only does the chance that any given bystander will intervene go down when there are more of them, but the chance that some bystander will intervene also falls with the number of bystanders? In other words, the dilution of the responsibility to intervene caused by the presence of others occurs so fast that it cannot be offset by the greater number of potential interveners.

In another experiment, theology students were told to prepare themselves to give a brief talk in a nearby building. One-half were told to build the talk around the Good Samaritan parable(!), whereas the others were given a more neutral topic. One group was told to hurry since the people in the other building were waiting for them, whereas another was told that they had plenty of time. On their way to the other building, subjects came upon a man slumping in a doorway, apparently in distress. Among the students who were told they were late, only 10 percent offered assistance; in the other group, 63 percent did so. The group that had been told to prepare a talk on the Good Samaritan was not more likely to behave as one. Nor was the behavior of the students correlated with answers to a questionnaire intended to measure whether their interest in religion was due to the desire for personal salvation or to a desire to help others. The situational factor - being hurried or not - had much greater explanatory power than any dispositional factor.

It would not be accurate to subsume this analysis, by saying that the students in the "hurry" category behaved the way they did because of a time constraint. Their constraint was not an objective or "hard" one, and in fact 10 percent of the students in this group did offer assistance. Rather, the situation shaped behavior by affecting the salience of competing desires. The face-to-face request enhances the strength of other-regarding motives, whereas being told to hurry diminishes it. Being able to see the reward that is imminently available makes it more attractive compared to one that will only be available with a delay, just as the sight of a beggar in the street can trigger generosity that the abstract knowledge of poverty would not. Kitty Genovese situations change both the perceived costs and perceived benefits of helping. The desire to comply with instructions by an impassive experimenter that "you must continue" to administer apparently painful and possibly fatal electrical shocks overrules the desire not to inflict pain needlessly.

There is no general or common mechanism by which a situation can affect behavior. Situations range from face-to-face demands to rescue Jews to the most trivial events, such as when finding a quarter in the coin return slot of a pay phone lifts one's mood and makes one help a stranger (in reality a confederate of the experimenter) retrieve a bunch of papers dropped on the sidewalk. The important lesson from these observations, in real life and in the laboratory, is merely that behavior is often no more stable than the situations that shape it. A person may be talkative at lunch when he can relax with long-standing colleagues and be tongue-tied with strangers. A person may consistently give to beggars but otherwise not give a thought to the poor. A person may invariably be helpful in situations in which nobody else can help, and invariably passive in the presence of other potential helpers. A man may be consistently aggressive and make biting remarks to his wife, yet be calm and generous to other people. His wife, too, may display the same dual behavior. His aggression triggers hers, and vice versa. If they rarely see the spouse interact with other adults, for example, at the workplace, they may believe that he or she is intrinsically aggressive rather than merely aggressive in the situation defined by their presence.”